Jib suspension



Sept. 2, 1969 (5. w. MORK 3,464,570

JIB SUSPENSION Filed July 14, 1967 \NVENTOR GEORGE W. MORK ATTORNEY United States Patent 3,464,570 .1118 SUSPENSION George W. Mork, South Milwaukee, Wis., assiguor to Bucyrus-Erie Company, South Milwaukee, Wis., a corporation of Delaware Filed July 14, 1967, Ser. No. 653,412 Int. Cl. B66c 23/64 US. Cl. 212-144 1 Claim ABSTRACT OF THE DISCLOSURE A boom, for example on a truck mounted crane, has a jib and a mast pivotally connected to its tip. A fixed suspension cable extends between the boom and the tip of the mast to hold the latter in a selected angular position. An adjustable suspension cable extends from the tip of the jib inwardly over the tip of the mast and is removably attached to the mast at one of several vertically spaced points on its rear surface, the particular point of attachment being chosen to give the jib one of several possible angular positions. The mast has vertical side rails and a plurality of vertically spaced, apertured crosspieces. The adjustable cable comprises parallel lines the inner ends of which are pivotally attached to the ends of a rigid equalizer bar. A clevis is fixed to and extends from the center of the bar and is adapted to receive the selected crosspiece, and a removable pin serves to pivotally attach the bar to the mast. The tip of the mast is provided with grooved arcuate guides for the adjustable cable lines, and holders extend across the grooves to prevent the lines from coming out of the grooves.

Background of the invention This invention relates to a jib suspension arrangement for a boom, for example on a truck mounted crane. A conventional suspension arrangement for a jib includes a first suspension cable or cables of fixed length between and fixed to the boom and the tip of a mast and a secand cable or set of cables of fixed length between the mast and the tip of the jib.

In many instances, especially in truck mounted cranes which must be capable of working in various environments, it is desirable to be able to vary the angle of the jib with respect to the boom in order to provide for changes in load or working conditions. Heretofore, it has been common to provide for such variation by substituting suspension cables of difierent lengths. This necessarily requires keeping extra cables on hand, and changing the angle of the jib requires disconnecting both ends of both sets of cables, all of which is expensive and a substantial nuisance. Coiling devices of various types have also been used to allow for jib angle adjustment, but these are also expensive and otherwise unsatisfactory,

Summary of the invention This invention contemplates a jib suspension in which there is a fixed suspension cable extending from a boom to the tip of the mast and an adjustable cable which leads from the tip of the jib over the tip of the mast and is attachable to the mast at any of several points on its rear surface, the particular point of attachment serving to determine the angle of the jib with respect to the boom. The specific embodiment of the invention shown is particularly satisfactory in that it allows for the use of a double adjustable cable with an equalizer bar that is readily attached to and removed from the mast. With the suspension arrangement of this invention, the angle of the jib can be changed simply by changing the "ice point of attachment of the adjustable cable to the mast, and it is unnecessary to provide alternative cables of various difierent lengths or expensive or complicated coil;- ing devices.

Brief description of the drawings FIG. 1 is a fragmentary, schematic side view showing the tip of a conventional boom with a mast and a jib attached thereto, a suspension arrangement according to this invention being incorporated therein,

FIG. 2 is an enlarged, fragmentary, exploded view in perspective further illustrating the jib suspension of FIG. 1, and

FIG. 3 is a fragmentary view in cross section through the plane 33 shown in FIG. 2.

Description of the preferred embodiment In FIG. 1, the reference numeral 1 refers to a conventional boom, only the tip of which is shown. It will be understood that the boom 1 is mounted, for example, on the revolving frame of a truck mounted crane (not shown). A generally conventional jib 2 and mast 3 are both pivotally connected at their inner ends or feet to the tip of the boom 1. A deflector sheave 4 is rotatably mounted on the mast 3, and a hoist cable 5 is trained over the sheave 4 and a hoist sheave 6 at the tip of the jib 2. By virtue of their pivotal connection with the boom 1, the jib 2 and mast 3 may of course be folded back for traveling.

As can be seen most clearly from FIG. 2, the mast 3 has a ladder-like construction including spaced parallel vertical side rails 7. Secured to and extending between the rails 7 there are three rearwardly facing, vertically spaced, L-shaped crosspieces 8 which are provided with central apertures 9 and which serve as alternative points of attachment for an adjustable jib suspension cable as will be described.

One or more fixed suspension cables 10 of appropriate length are suitably attached to the boom 1 and extend to and are connected to apertured anchors 11 at the tip of the mast 3, the cables 10 serving to maintain the mast 3 in a fixed angular relationship with respect to the boom 1. An adjustable suspension cable designated generally by the reference numeral 12 is fixed to and extends from the tip of the jib 2 inwardly over the tip of the mast 3 and is attached to any one of the crosspieces 8.

As can be seen from FIG. 2, the cable 12 actually comprises two parallel lines 13, the outer ends of which are suitably attached to the tip of the jib 2. The inner ends of the lines 13 are pivotally connected by means of fittings 14 to the ends of a rigid equalizer bar 15. A clevis 16, formed by welding or otherwise securely attaching plates to opposite sides of the bar 15, extends downwardly or rearwardly from the bar 15 and is provided with aligned apertures 17. The clevis 16 is of course capable of receiving any of the crosspieces 8 between its arms, and a headed pin 18 is removably received through the apertures 17 and 9 to removably pivotally attach the bar 15, and therefore the cable 12, to the mast 3. A cotter pin 19 is used to lock the pin 18 in place.

Generally semicircular grooved guides 20 ate fixed to a crossbar 21 extending between the ends of the mast side rails 7, and the lines 13 are trained about the guides 20 to hold them in place and keep them from kinking. Suitable holders 22 are attached to and extend across the grooves of the guides 20 to keep the lines 13 in place.

The choice of which crosspiece 8 the cable 12 is attached to will of course determine the angle of the jib 2 with respect to the boom 1. In the full line showing in FIG. 1, the bar 15 and cable 12 are attached to the middle crosspiece 8, and the jib 2 has approximately a 15 offset with respect to the boom 1. If the cable 12 were to be attached to the lowest crosspiece 8, the jib 2 would assume the upper position shown in dotted lines in FIG. 1 with no offset, and if the uppermost crosspiece 8 were chosen the jib 2 would assume the lowermost position shown in phantom lines, giving it approximately a 30 offset.

The angle of the jib 2 can be changed at any time simply by lowering the boom 1, removing the pin 18 to disconnect the bar from the mast 3 and reconnecting it at one of the other crosspieces 8. Obviously, any suitable number of crosspieces can be provided to give a suitable range of angles for the jib 2. Connection and disconnection are accomplished easily since it is only necessary to remove the single pin 18. The holders 22 serve to prevent the lines 13 from coming off the guides during adjustment, or when the jib 2 and mast 3 are folded back on the boom 1.

The twin line cable arrangement shown is particularly satisfactory for large machines, but it still provides for simple jib angle adjustment. The load on the two lines 13 is equalized because of their pivotal connection with the bar 15 and its pivotal connection with the selected crosspiece 8.

Although a preferred embodiment of the invention has been shown and described herein, it will be obvious that modifications might be made without departure from the scope of the invention.

I claim:

1. In an adjustable jib structure for a crane having a boom supported on one end with a tip end projecting outwardly and upwardly from said supported end, a jib 'with an inner foot end pivotally supported on said boom tip end to project therefrom at an angle, and a hoist cable sheave mounted at the outer end of the jib with a hoist cable suspended therefrom, the combination therewith of:

a mast having a foot end and a top end, said foot end being supported by said boom and being pivotally mounted at said boom tip, said mast top end extending in a generally upwardly direction from said boom tip and said mast having a ladder-like construction with two substantially parallel side rails extending from foot to top and a plurality of crosspieces end mounted between said side rails at spaced locations between said foot and top of said mast, said crosspieces each having a central attachment;

a mast support cable extending between said boom and said top of said mast to support said mast with respect to said boom;

21 pair of laterally spaced arcuate cable guides mounted on said top of said mast;

an equalizer bar having cable fittings pivotally mounted on its ends, and a central fastening means to pivotally fasten said equalizer bar to a central attachment on any selected crosspiece of said mast; and

a pair of jib support cables having inner and outer ends, said inner ends being fastened respectively to said cable fittings on the ends of said equalizer bar, said outer ends being fastened to said outer end of said jib to support said outer end of said jib in selected angular positions, and said cables being supported over said arcuate cable guides on said top of said mast.

References Cited UNITED STATES PATENTS 3,125,227 3/1964 Kauffman 212144 3,176,854 4/1965 Brown 212144 FOREIGN PATENTS 550,498 1/ 1943 Great Britain. 629,178 9/ 1949 Great Britain.

EVON C. BLUNK, Primary Examiner HARVEY C. HORNSBY, Assistant Examiner 

